Skip to Content

Purifying Water with Nano-particles

A company says 3-D nanoparticles boost the efficiency of water purification.
September 29, 2008

Adding nanoparticles to a water purifying membrane can double its efficiency, according to a startup company based in Los Angeles. With global water usage on the increase and fresh water in limited supply, the company, NanoH2O, says its novel approach could make such purification technology a viable solution to a growing problem.

Under pressure: The membrane developed by NanoH2O allows more water to filter through under for the same amount of pressure. This reduces energy requirements by around 20 percent, says CEO Jeff Green.

Reverse osmosis–feeding water through a semipermeable membrane to filter out impurities–is widely considered to be the most effective way to desalinate water. But it is very energy-intensive, and therefore expensive, because water has to be forced through the membrane under pressure. A key way to reduce the costs involved is to increase the water throughput for the same pressure. But for many years, improvements in membrane technology have been incremental at best, says Jeff Green, NanoH2O founder and CEO.

NanoH2O has found that adding porous nanoparticles to membranes can dramatically increase the efficiency with which water can be filtered. “Under similar pressure, twice as much water goes through,” says Green. In a desalination plant, this increased permeability would reduce energy requirements by 20 percent, or increase water productivity by 70 percent for the same cost, he adds.

“The concept is good,” says Benito Mariñas, an environmental engineer at the University of Illinois at Urbana-Champaign. Membrane-based desalination is usually considered only when freshwater supplies fail to meet demand. But with demand on the increase and only 1 percent of global freshwater available for human use, Mariñas says such technologies will become more important. “Right now we are not using membranes for sea water desalination as much as we could,” he says, largely due to the amount of energy required.

The material used for reverse osmosis is usually an organic thin-film membrane, typically a polymide material perforated with tiny holes. These holes are small enough to let water pass through, but they block salt and other contaminants. NanoH2O’s approach, based on research carried out by Eric Hoek, an environmental engineer at the University of California, Los Angeles, is to embed cage-like nanoparticles made out of aluminosilicate minerals, called zeolites, into the membrane. These particles have a diameter of no more than 200 nanometres–roughly equivalent to the thickness of the membrane.

Embedding the nanoparticles changes the properties of the membrane, making it hydrophilic, or water-attracting, so that water passes through more easily. Crucially, however, the membrane retains its ability to filter out contaminants, Green says.

NanoH2O has been in a research phase since the company was set up in 2005. But earlier this month, it secured $15 million in funding to commercialize its technology. According to Green, the company will now scale up production with the aim of bringing its technology to market by 2010.

Mariñas says there’s been plenty of interest in using inorganic hydrophilic materials for reverse osmosis, but no other design has been commercialized. One reason for this, he says, is that most hydrophilic materials tend to be bad at filtering out impurities. “The fact that this company is producing a hybrid that’s not made exclusively out of hydrophilic material is very interesting,” he says.

Another key advantage, says Green, is that the nanoparticles developed by NanoH2O have a three-dimensional porous structure. This means that unlike some other porous hydrophilic materials being investigated, there is no need to worry about how they are oriented within the membrane in order to pass water.

NanoH2O’s embedded approach is also compatible with existing manufacturing processes, Green says, adding just 5 percent to production costs.

Keep Reading

Most Popular

conceptual illustration of a heart with an arrow going in on one side and a cursor coming out on the other
conceptual illustration of a heart with an arrow going in on one side and a cursor coming out on the other

Forget dating apps: Here’s how the net’s newest matchmakers help you find love

Fed up with apps, people looking for romance are finding inspiration on Twitter, TikTok—and even email newsletters.

computation concept
computation concept

How AI is reinventing what computers are

Three key ways artificial intelligence is changing what it means to compute.

still from Embodied Intelligence video
still from Embodied Intelligence video

These weird virtual creatures evolve their bodies to solve problems

They show how intelligence and body plans are closely linked—and could unlock AI for robots.

We reviewed three at-home covid tests. The results were mixed.

Over-the-counter coronavirus tests are finally available in the US. Some are more accurate and easier to use than others.

Stay connected

Illustration by Rose WongIllustration by Rose Wong

Get the latest updates from
MIT Technology Review

Discover special offers, top stories, upcoming events, and more.

Thank you for submitting your email!

Explore more newsletters

It looks like something went wrong.

We’re having trouble saving your preferences. Try refreshing this page and updating them one more time. If you continue to get this message, reach out to us at customer-service@technologyreview.com with a list of newsletters you’d like to receive.